// MIT License

// Copyright (c) 2019 Erin Catto

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.

#include "box2d/b2_stack_allocator.h"
#include "box2d/b2_math.h"

b2StackAllocator::b2StackAllocator()
{
  m_index = 0;
  m_allocation = 0;
  m_maxAllocation = 0;
  m_entryCount = 0;
}

b2StackAllocator::~b2StackAllocator()
{
  b2Assert(m_index == 0);
  b2Assert(m_entryCount == 0);
}

void* b2StackAllocator::Allocate(int32 size)
{
  b2Assert(m_entryCount < b2_maxStackEntries);
  const int32 roundedSize = (size + ALIGN_MASK) & ~ALIGN_MASK;
  b2StackEntry* entry = m_entries + m_entryCount;
  entry->size = roundedSize;
  if (m_index + roundedSize > b2_stackSize)
  {
    entry->data = (char*)b2Alloc(roundedSize);
    entry->usedMalloc = true;
  }
  else
  {
    entry->data = m_data + m_index;
    entry->usedMalloc = false;
    m_index += roundedSize;
  }

  m_allocation += roundedSize;
  m_maxAllocation = b2Max(m_maxAllocation, m_allocation);
  ++m_entryCount;

  return entry->data;
}

void* b2StackAllocator::Reallocate(void* p, int32 size)
{
  b2Assert(m_entryCount > 0);
  b2StackEntry* entry = m_entries + m_entryCount - 1;
  b2Assert(p == entry->data);

  int32 incrementSize = size - entry->size;
  if (incrementSize > 0)
  {
    if (entry->usedMalloc)
    {
      void* data = b2Alloc(size);
      memcpy(data, entry->data, entry->size);
      b2Free(entry->data);
      entry->data = (char*)data;
    }
    else if (m_index + incrementSize > b2_stackSize)
    {
      void* data = b2Alloc(size);
      memcpy(data, entry->data, entry->size);
      m_index -= entry->size;
      entry->data = (char*)data;
      entry->usedMalloc = true;
    }
    else
    {
      m_index += incrementSize;
      m_allocation += incrementSize;
      m_maxAllocation = b2Max(m_maxAllocation, m_allocation);
    }
    entry->size = size;
  }

  return entry->data;
}

void b2StackAllocator::Free(void* p)
{
  b2Assert(m_entryCount > 0);
  b2StackEntry* entry = m_entries + m_entryCount - 1;
  b2Assert(p == entry->data);
  if (entry->usedMalloc)
  {
    b2Free(p);
  }
  else
  {
    m_index -= entry->size;
  }
  m_allocation -= entry->size;
  --m_entryCount;

  p = nullptr;
}

int32 b2StackAllocator::GetMaxAllocation() const
{
  return m_maxAllocation;
}
